Adhesive composition of matter



Patented May 23, 1944 ADHESIVE COMPOSITION OF MATTER Gerry Mack, JacksonHeights, N. Y., assignor to Advance Solvents and Chemical Corporation, acorporation of New York No Drawing. Application November 28, 1941,Serial No. 420,811

Claims.

My invention relates to compositions of matter having adhesivequalities, and more particularly to pressure sensitive adhesives.

Pressure sensitive adhesives have been known heretofore, but in a numberof instances these compositions have suffered from the disadvantage ofbeing fairly unstable, particularly when exposed to the action of air.Accordingly, it is one of the objects of this invention to provide apressure sensitive adhesive composition which will have superiorstability and which will retain its adhesive properties when exposed toair.

Also, amongst heretofore known pressure sensitive adhesive compositions,a number suffered from the disadvantage that they were not transparent,a property which is highly desirable. Accordingly, it is another of theobjects of this invention to provide a pressure sensitive compositionthat will be transparent and clear when it is associated with sheets orfilms of Cellophane (regenerated cellulose), cellulose acetate, ethylcellulose, cellulose nitrate, Pliofilm (rubber hydrochloride), andsimilar clear flexible sheet like materials. The adhesive, of course,can also be applied to fibrous materials such as paper and latex treatedpaper.

Amongst the drawbacks of some previously known pressure sensitiveadhesive compositions has been the characteristic property that theadhesive was offsetting, that is to say, that the adhesive sheet or filmwhen removed from surfaces to which it was supposedly temporarilyapplied would leave the adhesive on the surface to which it hadpreviously adhered. Accordingly, it is another of the objects of myinvention to provide a non-offsetting adhesive, so that the pressuresensitive adhesive sheet or film may be removed from surfaces to whichit is temporarily applied without leaving the adhesive on the surface.

Another of the objects of my invention is to provide an adhesivecomposition which will adhere under the force of pressure to any desireddry and clear surface, such as metal, glass, wood, lacquered or paintedsurfaces and the like.

It will be appreciated that such a pressure sensitive adhesivecomposition also may be used for making masking tape, tabs, displaycards, and similar articles, which can be attached to any desiredsurface by pressing them onto such surface, and to which they willadhere for a reasonable length of time, even when exposed to the actionof strong light, such as direct sunlight.

In general, the essential ingredients of the adhesive composition are arubber like polymer of isobutylene having a molecular weight higher than30,000 and in the preferred embodiment within the range from about90,000 to 200,000, a lower molecular weight polymer of isobutylenehaving a molecular weight higher than 1,000 and in the preferredembodiment within the range between 1,000 to 7,000, a non-volatileplasticizer such as methyl abietate or hydrogenated methyl abietate, aresin from the class of rosin ester gums, coumarone inden polymers,hydrogenated coumarone indene resins, terpene polymers, or from thefamily of natural resins, such as dammar and preferably dewaxed dammarresin, and a selected fatty mono-ester which acts as a stabilizer forthe adhesive composition.

The rubber like polymers of isobutylene can be prepared readily bypolymerizing isobutylene at low temperatures in the presence of avolatilizable inorganic halide as a catalyst. The temperature may bewithin the range of 5 C. and 0., depending upon the particular catalystused and the type of polymer desired.

A low polymer of isobutylene can be prepared by polymerizing at atemperature of about 10 C. by bubbling boron fluoride gas through asolution of isobutylene dissolved in propane. A polymer within the rangeof between 4,000 to 6,000 molecular weight may be prepared in thismanner and the volatile solvent may be removed by distillation, afterwhich the polymer can be washed with water or dilute caustic soda to remove any residual catalyst.

A polymer having a much higher molecular weight, that is above 30,000,and within the range of 90,000 to 200,000, if desired, can be made bypolymerizing isobutylene in the presence of boron fluoride at lowertemperatures, such as a 50 C. or even a C., using a substantially pureisobutylene as starting material and a substantially pure boron fluorideas a catalyst, and preferably carrying out the polymerization in thepresence of a suitable solvent for the isobutylene, such as purifiedethylene or other low boiling liquefied hydrocarbons.

It will be appreciated that the method of preparing the isobutylenepolymers per se is given for the purposes of exemplification, and doesnot of itself comprise a part of the invention. The prior art hasdisclosed the preparation of these polymers and reference may be had,for instance, to United States Patents Nos. 2,138,895 and 2,203,873 asindicative.

The non-volatile plasticizers that may be used in the preparation of theadhesive composition according to this invention should be compatiblewith all of the other ingredients present, and I found that thefollowing substances can be used advantageously, although it will beunderstood that I am not limited to the use of these particularmaterials:

Methyl abietate. di hydro methyl abietate,

Di ethylene glycol diabietate', chlorinated di phenyl (liquid type),rosin oil, abietyl alcohol,

Poly vinyl methyl ether, poly vinyl ethyl ether,

Poly viny1 isobutyl ether, liquid polymers of beta pinene,

Pine oil, mineral oil.

The stabilizer which, according to my invention, is added to thepressure sensitive composition, is a liquid fatty mono-ester formed bythe reaction of a fat acid with a monohydric aliphatic compound selectedfrom the group consisting of the normal primary alcohols and theirglycol monoethers. These fatty esters have been found to have aparticularly good stabilizing influence on the adhesive composition,especially regarding to its stability under the action of sun and air.The fatty acid esters of the mono-alkyl ethers of ethylene glycol havebeen found to give superior results, although it will be appreciatedthat I am not limited to the use of these particular esters. Thefollowing compounds are illustrative of the class of fatty esters whichhave been found to give satisfactory results:

Butyl stearate Mono-methyl ether of ethylene glycol ricinoleateMono-methyl ether of ethylene glycol palmitate Mono-butyl ether ofethylene glycol stearate Mono-ethyl ether of ethylene glycol ricinoleateMono-ethyl ether of ethylene glycol oleate Mono-amyl ether of ethyleneglycol stearate.

Rosin; hydrogenated rosin; ester gum;

Hydrogenated coumarone-indene resins;

Cycloparaifin resins; terpene diene polymer resins;

Dammar resin; chlorinated diphenyl resins;

Poly vinyl hydroabietanol resin.

It will be understood that by varying the proportions of the ingredientsused it is possible to produce a pressuie sensitive adhesive compositionhaving adhesive properties of the character hereinbefore described. Thecomposition may be compounded by dissolving the constituent ingredientsin a suitable solvent such, for instance, as toluol, benzene, naphtha,chlorinated hydrocarbons, and similar solvents, and then the dissolvedcomposition may be applied to the desired surface, film or fibrousmaterial.

The following examples in which the parts are by weight describe indetail some of the adhesive compositions which have been prepared inaccordance with the hereinbefore described method.

Example I Parts Isobutylene polymer (mol. wt. 95,000)

Isobutylene polymer (mol. wt. 3,000) L 6 Beta pinene polymer resin (M.P. 100 C.) 6

Parts Dihydro methyl abietate 4 Monobutyl ether of ethylene glycolstearate- 3 6 Naphtha (B. P. 110-275 F.) 200 The above ingredients areplaced in a churn and mixed until homogeneous.

In formulating these adhesives, the isobutylene high molecular weightpolymer serves as a rubbery" base for the adhesive, the resin serves togive adhesion and tack, and the working properties are given by theamount of plasticizer and tackifier, such as the methyl abietate. Thelength of the pull or legs, as it is known in the adhellB sive art, canbe adjusted by the amount of low molecular weight isobutylene polymerpresent, although this is not essential to the invention.

The above composition forms a particularly clear and transparentpressure sensitive adhesive go composition and is particularly adaptedfor use in masking tapes, having a transparent film as the support.

The above composition, when coated on a cellulose acetate filmto give amasking tape of the transparent type is particularly stable when exposedto sunlight. For instance, the same composition without the fatty ester,when exposed to sunlight transmitted through a window, became hazy andlost its pressure sensitive qualities in four days; the composition withthe fatty ester (mono-butyl ether of ethylene glycol stearate) under thesame conditions was still in excellent condition at the end of ten days,showing that the fatty ester was in some fashion acting as a stabilizerfor the adhesive composition.

While I cannot ofier an explanation as to why the fatty esters shouldact as stabilizers for such adhesive compositions, it is apparent fromabove example that a superior adhesive composition is obtained by usingthe fatty acids in the adhesive compositions and a new and unforeseeableresult is obtained through the use of such fatty esters.

Example II Parts Isobutylene polymer (mol. wt. 200,000) 10 Isobutylenepolymer (mol. wt. 7,000) 15 Hydrogenated rosin resin 2 Methyl abietate 3Butyl stearate 5 Carbon tetrachloride 100 Naphtha 60 5 The ingredientswere placed in a churn and mixed until homogeneous.

The same sunlight exposure test was made as in Example #I, and again thecomposition with the butyl stearate was superior in its retention 60 ofadhesive qualities as compared to same composition without the fattyester.

The adhesive compositions described herein, when coated on cellulosefilm as is done in the cellulose tape field, not only were superior inretaining their original pressure sensitive qualities when exposed tostrong sunlight, but were also superior in ordinary shelf agingtests, 1. e. making up a finished roll of the masking tape andperiodically observing the retention of original pressure sensitiveproperties with time. Without the fatty ester present, the adhesivecomposition would have a tendency to become somewhat brittle and dry atend of six weeks, whereas with the fatty acid present, the adhesivecomposition was still in good condition at the end of five months.

Example III Percent by weight Parts Liquid or semi-liquid polymer ofisobutyl- Isobutylene polymer (moi. wt. 60,000) 15.0 9 between 1,000 toHydrogenated rosin 2.5 Resle Dihydro methyl abietate 2.5 5 Plastlelzer220 Butyl stearate 2.0 Fatty ester Naphtha 1500 It will be apparent fromthe foregoing descrip- The mixing was performed as in the previous tionthat an excellent stabilizer for an isobutylene examples. The samesuperior properties as in m polymer adhesive has been provided.Furtherprevious examples were observed. more, it will be obvious tothose skilled in the The presence of the low polymer of isobutylene artthat various minor modifications may be is not essential to the makingof a good pressure made in the invention without departing fromsensitive adhesive composition, although it is the spirit of theinvention, and accordingly I advantageous where best aging qualities aswell 15 claim all such modifications which fall fairly as good workingqualities are required. Similar within-the spirit and scope of thehereinafter softeners and plasticizers as previously menappended claims.tioned, namely liquid polymers of chlorinated WhatIclaim is: diphenyl,rosin oils, vinyl ethers, and even min- 1. A stabilized, pressuresensitive, adhesive era] oil can be used in place of the low polymercomposition comprising a high molecular weight of isobutylene. In placeof the low polymers of polyisobutylene, a thermoplastic adhesion andisobutylene there can be used synthetic hydrotack producing resin, anon-volatile plasticizer, carbon oils such as described in U. S. Patentand, as a stabilizer, a liquid fatty mono-ester 2,224,349. Thesesynthetic oils are viscous liquids formed by'the reaction of a, fat acidwith a monoand chemically consist of both normal olefines and hydricaliphatic compound selected from the iso olefines which have beenpolymerized as degroup consisting of the normal primary alcoscribed inthis above mentioned patent. The syn hols and their glycol monoethers.thetic oils suitable for my use are those having a' 2. A stabilized,pressure sensitive, adhesive viscosity of from 50 to 10,000 seconds, asmeascomposition comprising a polyisobutylene having ured at 210 F. bythe Universal Saybolt method. a molecular weight above 30,000, apolyisobutyl- The type of pressure sensitive adhesive desired ene havinga molecular weight between 1000 and will govern the choice of materialsused. 7000, a thermoplastic adhesion and tack producing resin, anon-volatile plasticizer, and, as Example IV a stabilizer, a liquidfatty mono-ester formed by Same as E a p e e p t & y the reaction of afat acid with a monohydric fin resin vi a melting Point Of 90 t0aliphatic compound selected from the group con- Was used in DlflCe theDinene polymer resin. sisting of the normal primary alcohols and theirExample V glycol monoethers.

' v 3. A composition of matter as claimed in claim same as Example #I xe that mono-ethyl 40 1, wherein said fatty esteris mono-butyl etherether of ethylene glycol ricinoleate was used in f ethylene glycolstearate place of the meno'butyl ether of ethylene glycol 4. Acomposition of matter as claimed in claim stearate. 1, wherein saidfatty ester is mono-methyl ether Where transparency is not required,coloring f ethylene glycol ricinoleata pigments pigments such as ZincOxide titanox' 5. A composition of matter as claimed in claim similarpigments can be used according to 1, wherein said fatty ester is butylstearate. sued fi In h case where Zinc Oxide is 6. Astabilized pressuresensitive adhesive comused, it will be noticed that a greater amountposition omprising 10 parts by weight of a pol of tack and adhesivenessoetamedr and Such isobutylene having an average molecular weight massesare usable for the surgical type of adheof 95,000 6 parts by weight of apolyisobutylene sive tapes where the additional zinc oxide gives ahaving an average molecular weight of 3 000 6 greater adhesiveness tothe adhesive composition. parts by weight of beta pinene polymer -g iMany other formulas can be used depending mg a melting point of 100 0,,4 parts by weight P the character of e e composition of dihydro methylabietate and, as a stabilizer, sired, the base upon which it 18 appliedand the 3 parts by weight of monmbutyl ether of ethyl purpose for whichit is to be utilized. The proene glycol stearate portions of theingredients can be vafied over a 7. A stabilized, pressure sensitive,adhesive wide range! and the essential agents combined compositioncomprising a high molecular weight either sfnglyy in eombiflaf'ionv oreempetiblc polyisobutylene, a thermoplastic adhesion and tures withothers of similar character stics. tack producing resin a nonwolatfleplasticizer' f gener I have felled that my pressure and as a stabilizer,an ester formed by the reacsitive adhesive c ompositionsmay contain then of a f t acid with an ethylene glycol monomgredlents prevlouslymenmonedi m ether of a primary aliphatic alcohol having from e renee ofproportions elven below and l to 5 carbon atoms in the alcohol radical.sun mamtam, parewulafly and trans 05 8. A stabilized, pressuresensitive, adhesive filial c:i b: se? n iefi zfi se fil rf 0 5 1 3:composition comprising a polyisobutylene, a thertransparent types offilm used in the industrv moplastlc adheswP-and tack producing-resinwhere trans arenc is desired i m non-volatile plasticizer, and, as astabilizer, befillers waxes and siinilar materials ear l ae tween 2% and15% by weight of a hquid fatty to giv'e a desired result 7 mono-esterformed by the reaction of a fat acid with a mono-hydric aliphaticcompound select- RANGE or PROPORTIONS ed from the group consisting ofthe normal pri- Percent by weight mary alcohols and their glycolmonoethers. Rubbery polymer of isobutylene (r1101. wt, 9. A stabilized,pressure sensitive, adhesive higher than 30,000) 10-70 75 compositioncomprising between 10% and by weight of a polyisobutylene having anaverage molecular weight above 30,000, between 0% and 70% by weightoi apolyisobutylene having an average molecular weight between 1,000 and7,000, between 5% and 30% by weight of a thermoplastic adhesion and tackproducing resin, between 2% and 20% by weight of a non-volatileplasticizer, and, as a stabilizer, between 2% and 1.5% by weight of aliquid fatty mono-ester formed by the reaction of a fat acid with amonohydric aliphatic compound selected from the group consisting of thenormal primary alcohols and their glycol monoethers.

10. A method of stabilizing pressure sensitive adhesivecompositiongcontaining a high molecular polyisobutylene, a thermoplasticadhesion and tack producing resin, and a non-volatile plasticizer, whichmethod comprises adding to a and intimately mixing with saidcompositions a stabilizer in the form of a liquid fatty monoester formedby the reaction of a fat acid with a monohydric aliphatic compoundselected from the group consisting of the normal primary al- 20 coholsand their glycol monethers, said sta-

